The present invention relates to novel balloon catheters for use in the treatment of vascular diseases and to methods of making and using the same.
Balloon catheters are employed in a variety of medical procedures. One such procedure is angioplasty which is a well known medical practice used in the treatment of diseased arteries in the vasculature of a patient. Using angioplasty procedures, alone, however, involves a risk of re-restenosis of the artery, which may necessitate another angioplasty procedure, a surgical bypass procedure, or some method of repairing or strengthening the area. Therefore, it has become more common practice to use a catheter-delivered stent to prevent restenosis and to reinforce and strengthen weakened vessel walls. Using this procedure, a physician can implant an intravascular device, i.e. a stent, to maintain vascular patency at the site of a lesion.
A stent is typically a generally cylindrical, radially expandable device which is introduced into the vasculature of a patient using a catheter delivery assembly which typically includes an elongate shaft with a dilatation balloon mounted on its distal portion. The stent is then mounted over the dilatation balloon. The stent is maneuvered through the vasculature of the patient in a generally reduced diameter configuration, i.e. crimped. Once it has been delivered to the site of the lesion, the stent is then expanded from its reduced diameter configuration to support and reinforce the vessel walls while maintaining the vessel in an open, unobstructed condition.
Stents are well-known and widely available in both self-expanding and inflation expandable varieties. Self-expanding stents are typically maintained under positive external pressure in order to maintain their reduced diameter configuration during delivery of the stent to its deployment site. Inflation expandable stents, i.e. balloon expandable stents, are crimped to their reduced diameter about the inflation member of the stent delivery catheter and once positioned at the deployment site are expanded to a larger diameter for implantation in the vasculature by providing inflation fluid to the inflation member thus expanding the inflation member thus expanding the stent.
One problem which may arise in the case of balloon expandable stents, is commonly referred to in the industry as xe2x80x9cwatermelon seedingxe2x80x9d in which the stent has been known to slide off the balloon during expansion. Various methods have been employed in order overcome the possibility of stent slippage during expansion.
The present invention relates to novel dilatation balloons which exhibit first and second inflation profiles, and to methods of producing the novel balloons of the present invention. The balloon has a body portion, cones and waist portions. The body of the balloon further has a proximal region and a distal region which are separated by the central region of the body. The length of the body, and the taper angle of the cone portions change from one inflation profile to the next as the pressure is increased.
The balloon has a first inflation profile achieved by inflating the balloon to a first inflation pressure and a second inflation profile which is achieved by increasing the inflation pressure to a second, higher pressure.
In one embodiment, in the first inflation profile of the balloon, the central region is inflatable to a diameter D1 and at least one of the proximal and distal regions of the body portion of the balloon are inflatable to a second diameter which is less than D1, D1xe2x80x2. The diameter D1xe2x80x2 may be taken at any of an infinitesimal number of locations between the central region of the balloon body and the cone portions. As the point at which D1xe2x80x2 is taken approaches the central region of the body portion, the value of D1xe2x80x2 will approach the value of D1. In the second inflation profile, the central region is inflatable to a diameter D1 xe2x80x3 and the proximal and/or distal ends of the body portion of the balloon are inflatable to a diameter D1xe2x80x3 which is substantially equal to D1. It is important to note that D1 may increase some nominal amount from the first inflation profile to the second inflation profile.
Thus, in the second inflation profile, the proximal region, the distal region or both, and the central region of the body portion have inflation diameters which are substantially constant along the length of the balloon body. In the first inflation profile, the proximal and/or distal ends of the body region taper into the cone regions.
The inflation of the balloon to its first inflation profile is achieved by inflation to a first pressure, and inflation to the second inflation profile is achieved by inflation to a second pressure higher than the first pressure
The present invention further relates to a method of making the same, the method including a first molding step wherein the second inflation profile or configuration is formed and a second molding step wherein the first inflation profile or configuration is formed.
In a first molding step at a temperature T1, the balloon is formed to have a body having a length L1 and tapered cones which have an angle Ø1 relative to the longitudinal axis of the balloon and in a second molding step at a temperature T2 which is less than T1 but higher than the Tg of the material from which the balloon is being formed, the balloon is remolded to have a body with a length L2 which is less than L1 and tapered cones which have an angle Ø2 relative to the longitudinal axis of the balloon which is less than Ø1. During inflation, the balloon exhibits the configuration formed during the second molding step at a first pressure, and exhibits the configuration formed during the first molding step at a second higher pressure. The balloon is thus said to have two inflation profiles, the first inflation profile being the second remolded configuration and the second inflation profile being the first molded configuration.
During inflation, as the pressure is increased to relatively low to medium pressure during expansion, the first inflation profile or configuration is exhibited. At higher pressures, the balloon reaches its fully expanded configuration and exhibits its second inflation profile or configuration.
The dilation balloons of the present invention may be used in various medical procedures and thus come in a large range of sizes and may therefore be suitably dimensioned for their intended purpose.
The balloon catheters of the present invention are particularly useful for the delivery and implantation of stents for use in the treatment of stenotic vascular disease. Furthermore, the present invention is particularly suitable for use with inflation expandable stents wherein enhanced stent securement and safer stent loading are of concern.
Using a catheter delivery assembly, the dilatation balloon of the present invention, in combination with the stent, is positioned adjacent a treatment site in a body vessel where it is first inflated to its first inflation profile at a first pressure wherein the central region is inflated to a diameter D1 and at least one of the proximal and distal ends of the body of the balloon is inflated to a diameter D1xe2x80x2 which is less than D1. The diameter D1xe2x80x2 may be taken at any infinitesimal number of points between the central region of the body and the cone portions. The balloon is then inflated to its second inflation profile at a second higher pressure wherein the central region of the body is inflated to D1, and the proximal and distal regions of the body are inflated to a diameter D1xe2x80x3 which is substantially equal to D1. However, as noted above, D1, in the second inflation profile, may be nominally larger than in the first inflation profile.
The balloon of the present invention may be employed in combination with various devices including catheter delivery devices and stents, for example, and may be employed in the treatment of various diseases.
Further features and advantages of the present invention will become apparent to one of skill in the art in view of the Detailed Description of the Preferred Embodiments which follows, when considered together with the attached drawings and claims.